We seek to study the nervous, hormonal and mechanical events involved in the regulation of gastric emptying and motility in dogs. Six different but related studies are planned to define this. 1. Studies will be made to determine the anatomical localisation in the small bowel of receptors responsive to osmotic pressure, fats and acids. This will be done using dogs with fistulas in the first 5 cm of duodenum, at the junction of duodenum and in the jejunum 60 cm from the ligament of Treitz. The index of gastric emptying in all studies will be the volume of the meal (with phenol red as a marker) left in the stomach at a set time. 2. Studies will be made to further localise the osmoreceptor in the brush or cell by using disaccharides and dipeptides. 3. Studies to determine the anatomical localisation of the receptor to L-tryptophane, the only amino acid shown to delay emptying by a non-osmotic mechanism. Also studies will be made of amino and carboxyl substitutions of tryptophane as well as examining its metabolic products. 4. Studies will be made in dogs and cats to determine the role of the pyloric sphincter in controlling emptying. Using a mechanical device placed in the pylorus to keep it open, emptying will be measured in response to water, acid and hypertonic glucose meals as well as in response to intravenous secretin. Comparisons will be made with the pyloric cannula in place and after its removal. In some studies a force strain gage transducer and monopolar electrode will be sewn to the serosal surface of the antrum and measurements made of the frequency and force of antral contractions and also slow wave frequency with the pylorus either kept open or in its normal state. 5. Studies of gastric emptying using dose-response techniques will be made with the polypeptides cerulein, pentagastrin, octapeptide of CCK, motilin and gastric inhibitory peptide. In some experiments electrodes and strain gage transducers will be used to measure motility and slow waves. 6. Studies of celiac ganglionectomy will be made to assess the neural mechanisms involved in the enterogastric reflex and how it affects emptying and motility.